The field of art to which this invention pertains is homopolymers and copolymers of vinylphenol.
Homopolymers and copolymers of 4-hydroxystyrene, or p-vinylphenol as it is also called, are known compositions which have many uses, such as in the manufacture of metal treatment compositions and photoresists. Polymers of p-vinylphenol can be made by polymerizing p-vinylphenol itself. However, p-vinylphenol is an unstable compound and must be refrigerated to prevent it from polymerizing spontaneously. Even under refrigeration, the monomer will slowly polymerize to low molecular weight polymers. 4-Acetoxystyrene, the acetic acid ester of p-vinylphenol, is a stable monomer which can be readily homopolymerized and copolymerized to low, medium and high molecular weight polymers. After polymerization, the phenolic ester group can be hydrolyzed to produce p-vinylphenol polymers.
Corson et. al., Journal of Organic Chemistry, 23, 544-549 (1958), describe a 5 step process for making p-vinylphenol from phenol. The phenol is first acetylated to p-hydroxyacetophenone which is then acetylated to p-acetoxyacetophenone. This compound is hydrogenated to p-acetoxyphenylmethyl carbinol which is then dehydrated to p-acetoxystyrene. The p-acetoxystyrene is saponified to p-vinylphenol using potassium hydroxide. Packham, in the Journal of the Chemical Society, 1964, 2617-2624, describes the hydrolysis of crosslinked poly-4-hydroxystyrene by refluxing the polymer in alkaline aqueous dioxane for 2 days. In U.S. Pat. No. 4,544,704, a copolymer of styrene and p-isopropenylphenylacetate is hydrolyzed with aqueous sodium hydroxide in methanol and toluene using a small amount of benzyltrimethylammonium chloride as a phase transfer agent. Arshady et. al., Journal of Polymer Science, 12, 2017-2025 (1974), hydrolyzed copolymers of styrene and acetoxystyrene to the vinylphenol polymer using hydrazine hydrate in dioxane.
The ester interchange reaction of poly (4-acetoxystyrene) in methanol using sodium methylate is described in U.S. Pat. No. 2,276,138. It is also stated in the patent that resinous polymers are obtained by the treatment of monomeric 4-acetoxystyrene with potassium hydroxide in methanol both cold and hot and with methanol using sulfuric acid as the ester interchange catalyst.
The hydrolysis or methanolysis of polymers of 4-acetoxystyrene is very difficult to carry to 90 percent or above completion. Also, it is extremely difficult to remove all traces of alkali metal salts which can be detrimental for some applications and uses of the vinylphenol polymer.